Plate Nº 57 · recorded October 10, 2026
Space & AstronomyReported finding
Roman telescope hits 1/100,000-degree stability in early tests
NASA's Roman Telescope held pointing stable to 1/100,000 of a degree in Sept. 2026 commissioning — like aiming a laser at a dime from 150 miles. Its coronagraph captured first cosmic starlight Sept. 22 and 27.
By Marcus Bennett4 min read761 words
In brief
- Roman held pointing stable to better than 1/100,000 of a degree during Sept. 15–21, 2026 commissioning tests
- The Wide Field Instrument contains 18 detectors, with sections reserved for guide-star tracking
- Roman's coronagraph received its first cosmic light on Sept. 22, 2026, capturing a faint star in the Large Magellanic Cloud
- The fine-guidance system updates four times per second, supporting 8-hour coronagraph exposures
- Engineers target a final pointing precision equivalent to aiming a laser at a dime from about 230 miles (370 km)
NASA's Roman Space Telescope held its pointing stable to better than 1/100,000 of a degree during Sept. 15–21, 2026 commissioning tests — a precision comparable to aiming a laser at a U.S. dime from about 150 miles.
That precision underpins the entire mission. The observatory's Wide Field Instrument, its primary science camera, contains 18 detectors. Engineers reserved a small section of each detector for tracking guide stars — reference points whose positions are already known with extreme accuracy.
"Every Roman observation relies on its ability to stay precisely pointed at the correct region of space long enough to collect an image, which can take from minutes to hours for a deep exposure," said Begoña Vila, Roman's guiding instrument systems lead at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
"The fine-guidance system reports the positions of the guide stars about four times each second to the attitude control system, which can move the observatory a tiny amount to counter any drift as needed," Vila said. "Our tests confirmed stability better than 1/100,000 of a degree for half an hour at a time for Wide Field Instrument observations or for eight hours at a time for Coronagraph Instrument observations."
With the Wide Field Instrument, that stability held for half-hour stretches. With the Coronagraph Instrument, it held for eight-hour windows. Engineers expect further tuning to extend the dime-laser analogy out to about 230 miles (370 kilometers).
How does the fine-guidance system work?
Roman's attitude control system first steers the spacecraft toward the right patch of sky. The fine-guidance system then continuously monitors chosen guide stars and feeds corrections back to the attitude controls. Without those adjustments, Roman's sharpest images would blur.
What does spectral guiding change?
Roman will test a guidance mode that has not been used this way before. Most space telescopes carry a dedicated guider instrument. Roman does not. Instead, it will lock onto the wavelength patterns — called spectra — of stars rather than their point-like appearance.
"Roman doesn't have a separate guider instrument, like other space telescopes do," Vila said. "Because Roman is already equipped to measure spectra for science, it can use that same information to precisely position the telescope. We are looking forward to validating this spectral guiding mode in the coming weeks."
Spectra contain information about how an object's light spreads across wavelengths. Using the same data for both science and guiding could simplify telescope designs on future missions.
What did the coronagraph see on its first night?
On Sept. 22 and Sept. 27, the team switched on Roman's Coronagraph Instrument. The coronagraph is meant to suppress the glare of nearby stars so astronomers can image the planets and dusty disks circling them.
The coronagraph first powered up on Sept. 1 and stretched its digital, electronic, and mechanical components mid-month. Those basic checks came before any cosmic light test.
On Sept. 22, the instrument pointed at a single faint star in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. Engineers kept the detectors warmer than their final operating temperature — a precaution to keep contaminants from sticking to the sensors.
"This observation confirms that the instrument can produce a focused image," said Vanessa Bailey, a Roman Coronagraph Instrument scientist at NASA's Jet Propulsion Laboratory in Southern California. "It's a very limited test that kicks off a methodical process of increasingly complex tasks that help us prepare for the instrument's future observations."
"We were kicking the tires, making sure light goes through the system," Bailey said.
On Sept. 27, the team cooled the detectors and pointed at a new patch in the Large Magellanic Cloud, where they expected to see many stars in a single image. They did.
"We're breathing a sigh of relief," Bailey said.
What's next for Roman?
The earliest coronagraph tests are part of a methodical commissioning campaign, not science observations. The instrument must still complete increasingly complex tasks before it can suppress starlight enough to reveal planets.
Even tiny vibrations could let starlight leak into an image and drown out the planets Roman aims to find. The coronagraph's internal stability process goes beyond the Wide Field Instrument, adding an extra layer of precision.
Commissioning will run for weeks. Each milestone — spectral guiding validation, deeper coronagraph tests, transition to science operations — adds another checkmark to Roman's checklist.
The mission is designed to survey the sky for microlensing exoplanets, map dark matter, and probe the infrared background.
via ScienceDaily: Space & Time (Source)
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